Enhanced heterozygosity from male meiotic chromosome chains is superseded by hybrid female asexuality in termites
Although males are a ubiquitous feature of animals, they have been lost repeatedly in diverse lineages. The tendency for obligate asexuality to evolve is thought to be reduced in animals whose males play a critical role beyond the contribution of gametes, for example, via care of offspring or provis...
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Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 118; no. 51 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
National Academy of Sciences
21.12.2021
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Subjects | |
Online Access | Get full text |
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Summary: | Although males are a ubiquitous feature of animals, they have been lost repeatedly in diverse lineages. The tendency for obligate asexuality to evolve is thought to be reduced in animals whose males play a critical role beyond the contribution of gametes, for example, via care of offspring or provision of nuptial gifts. To our knowledge, the evolution of obligate asexuality in such species is unknown. In some species that undergo frequent inbreeding, males are hypothesized to play a key role in maintaining genetic heterozygosity through the possession of neo-sex chromosomes, although empirical evidence for this is lacking. Because inbreeding is a key feature of the life cycle of termites, we investigated the potential role of males in promoting heterozygosity within populations through karyotyping and genome-wide single-nucleotide polymorphism analyses of the drywood termite
We showed that males possess up to 15 out of 17 of their chromosomes as sex-linked (sex and neo-sex) chromosomes and that they maintain significantly higher levels of heterozygosity than do females. Furthermore, we showed that two obligately asexual lineages of this species-representing the only known all-female termite populations-arose independently via intraspecific hybridization between sexual lineages with differing diploid chromosome numbers. Importantly, these asexual females have markedly higher heterozygosity than their conspecific males and appear to have replaced the sexual lineages in some populations. Our results indicate that asexuality has enabled females to supplant a key role of males. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 1Present address: Koshi Research Station, Institute for Plant Protection, National Agriculture and Food Research Organization, Koshi 861-1192, Japan. Edited by Raghavendra Gadagkar, Centre for Ecological Sciences, Indian Institute of Science, Bangalore, India; received May 13, 2020; accepted November 2, 2021 Author contributions: T.Y., K.M., and N.L. designed research; T.Y., N.M., and S.H. provided resources; T.Y., Y.-K.T., T.N., N.M., and S.H. performed experiments; T.Y., Y.-K.T., C.V.D.W., and N.L. analyzed data; T.Y. and N.L. wrote the paper; and T.Y., Y.-K.T., C.V.D.W., T.N., N.M., S.H., K.M., and N.L. contributed substantially to revisions. |
ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.2009533118 |